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arXiv 1108.0372cond-mat.mtrl-sci
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锂硅中应力-电势耦合的原位测量

In Situ Measurements of Stress-Potential Coupling in Lithiated Silicon

Vijay A. Sethuraman, Venkat Srinivasan, Allan F. Bower, Pradeep R. Guduru

摘要:

分析了锂硅电极的应力状态与电势的关系。基于固溶体的Larché和Cahn化学势,从热力学角度论证了锂化硅中存在应力-势耦合;基于材料的已知性质,估计耦合的大小为ca. 60 mV/GPa的薄膜几何形状。对硅薄膜电极进行了实验研究,在电化学锂化和脱锂过程中原位测量了应力。通过增量脱锂逐步改变应力,测得应力变化和电势变化之间的关系为100 - 120 mV/GPa,这与分析预测的数量级相同。耦合的重要性进行了讨论,在解释中观察到的滞后电位与充电状态图,和应力的作用,在修改的硅电极的最大充电容量的压力下。

英文摘要:

An analysis of the dependence of electric potential on the state of stress of a lithiated-silicon electrode is presented. Based on the Larché and Cahn chemical potential for a solid solution, a thermodynamic argument is made for the existence of the stress-potential coupling in lithiated-silicon; based on the known properties of the material, the magnitude of the coupling is estimated to be ca. 60 mV/GPa in thin-film geometry. An experimental investigation is carried out on silicon thin-film electrodes in which the stress is measured in situ during electrochemical lithiation and delithiation. By progressively varying the stress through incremental delithiation, the relation between stress change and electric-potential change is measured to be 100 - 120 mV/GPa, which is of the same order of magnitude as the prediction of the analysis. The importance of the coupling is discussed in interpreting the hysteresis observed in potential vs. state-of-charge plots, and the role of stress in modifying the maximum charge capacity of a silicon electrode under stress.

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